Ethylene separation

ABSTRACT

A polyethylene production process, comprising contacting ethylene and a polymerization catalyst under suitable reaction conditions to yield a polymerization product stream, separating a light gas stream from the polymerization product stream, wherein the light gas stream comprises ethane and unreacted ethylene, contacting the light gas stream with an absorption solvent system, wherein at least a portion of the ethylene from the light gas stream is absorbed by the absorption solvent system, removing unabsorbed gases of the light gas stream from contact with the absorption solvent system to form a waste gas stream, and recovering ethylene from the absorption solvent system.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND

1. Field of the Invention

This invention generally relates to the production of polyethylene. Morespecifically this invention relates to systems and processes forimproving polyethylene production efficiency by decreasing ethylenelosses.

2. Background of the Invention

The production of polymers such as polyethylene from light gasesrequires a high purity feedstock of monomers and co-monomers. Due to thesmall differences in boiling points between the light gases in such afeedstock, industrial production of a high purity feedstock may requirethe operation of multiple distillation columns, high pressures, andcryogenic temperatures. As such, the energy costs associated withfeedstock purification represent a significant proportion of the totalcost for the production of such polymers. Further, the infrastructurerequired for producing, maintaining, and recycling high purity feedstockis a significant portion of the associated capital cost.

In order to offset some of the costs and maximize production, it can beuseful to reclaim and/or recycle any unreacted feedstock gases,especially the light hydrocarbon reactants, such as ethylene. Gasescomprising unreacted monomers may be separated from the polymer afterthe polymerization reaction. The polymer is processed while theunreacted monomers are recovered from the gases that are reclaimedfollowing the polymerization reaction. To accomplish this, the reclaimedgas streams have conventionally either been routed through apurification process or redirected through other redundant processingsteps. In either case, conventional processes of recovering monomer havenecessitated energetically unfavorable and expensive processes.

Consequently, there is a need for high-efficiency separation of ethylenefrom a recycle stream.

BRIEF SUMMARY

A polyethylene production process, comprising contacting ethylene and apolymerization catalyst under suitable reaction conditions to yield apolymerization product stream, separating a light gas stream from thepolymerization product stream, wherein the light gas stream comprisesethane and unreacted ethylene, contacting the light gas stream with anabsorption solvent system, wherein at least a portion of the ethylenefrom the light gas stream is absorbed by the absorption solvent system,removing unabsorbed gases of the light gas stream from contact with theabsorption solvent system to form a waste gas stream, and recoveringethylene from the absorption solvent system.

A polyethylene production process, comprising contacting ethylene and apolymerization catalyst in a polymerization reactor under suitablereaction conditions to yield a polymerization product stream, separatinga light gas stream from the polymerization product stream, wherein thelight gas stream comprises ethane and unreacted ethylene, contacting thelight gas stream with an absorption solvent system in an absorptionvessel, wherein at least a portion of the ethylene from the light gasstream is absorbed by the absorption solvent system to yield acomposition comprising a complex of the absorption solvent system andethylene, and removing the unabsorbed gases of the light gas stream fromcontact with the absorption solvent system.

A polyethylene production system, comprising a feed stream comprisingethylene introduced into a first polymerization reactor, apolymerization product stream emitted from the first polymerizationreactor and introduced into a separator, a light gas stream comprisingunreacted ethylene emitted from the separator, the light gas streambeing separated from the polymerization product stream and introducedinto an absorption reactor comprising an absorption solvent system, anabsorbent-ethylene conjugant, wherein the conjugant is formed fromunreacted ethylene absorbed by the absorption solvent system, and awaste gas stream comprising ethane, wherein the waste gas streamcomprises components of the light gas stream that are not absorbed bythe absorption solvent system.

The foregoing has outlined rather broadly the features and technicaladvantages of the invention in order that the detailed description ofthe invention that follows may be better understood. The variouscharacteristics described above, as well as other features, will bereadily apparent to those skilled in the art upon reading the followingdetailed description of the preferred embodiments, and by referring tothe accompanying drawings.

DESCRIPTION OF THE DRAWINGS

For a detailed description of the preferred embodiments of theinvention, reference will now be made to the accompanying drawings inwhich:

FIG. 1 illustrates a schematic of a first embodiment of a polyethyleneproduction system;

FIG. 2 illustrates a schematic of a second embodiment of a polyethyleneproduction system;

FIG. 3 illustrates a schematic of a third embodiment of a polyethyleneproduction system;

FIG. 4 illustrates a flow diagram of a first embodiment of apolyethylene production process;

FIG. 5 illustrates a flow diagram of a second embodiment of apolyethylene production process;

FIG. 6 illustrates a flow diagram of a third embodiment of apolyethylene production process; and

FIG. 7 illustrates a schematic of an embodiment of a simulatedpolyethylene production system.

DETAILED DESCRIPTION

Disclosed herein are systems, apparatuses, and processes related to theproduction of polyethylene with improved efficiency. The systems,apparatuses, and processes are generally related to the separation of afirst chemical component or compound from a composition resulting fromthe production of polyethylene and comprising the first chemicalcomponent or compound and one or more other chemical components,compounds, or the like.

Referring to FIG. 1, a first polyethylene production (PEP) system 100 isdisclosed. PEP system 100 generally comprises a purifier 102, reactors104, 106, a separator 108, a processor 110, an absorption reactor 116,and a flare 114. In the PEP embodiments disclosed herein, various systemcomponents may be in fluid communication via one or more conduits (e.g.,pipes, tubing, flow lines, etc.) suitable for the conveyance of aparticular stream, for example as show in detail by the numbered streamsin FIGS. 1-3.

In the embodiment of FIG. 1, a feed stream 10 may be communicated to thepurifier 102. A purified feed stream 1 may be communicated from thepurifier 102 to one or more of the reactors 104, 106. Where such asystem comprises two or more reactors, a reactor stream 15 may becommunicated from reactor 104 to reactor 106. A polymerization productstream 12 may be communicated from one or more of the reactors 104, 106to the separator 108. A polymer stream 14 may be communicated from theseparator 108 to the processor 110. A product stream 16 may be emittedfrom the processor 110. A gas stream 18 may be communicated from theseparator 108 to the absorption reactor 116. A waste stream 20 may becommunicated from the absorption reactor 116 to the flare 114 and arecycle stream 22 may be communicated from the absorption reactor 116 tothe separator 108. A reintroduction stream 24 may be communicated fromthe separator 108 to the purifier 102.

Referring to FIG. 2, a second PEP system 200 is disclosed, which has anumber of system components common with PEP 100. In the alternativeembodiment illustrated by FIG. 2, the second PEP system 200 additionallycomprises a deoxygenator 118. Alternatively to the first PEP system 100(as illustrated in FIG. 1), in the embodiment illustrated by FIG. 2, thegas stream 18 may be communicated to the deoxygenator 118. A treated gasstream 26 may be communicated from the deoxygenator 118 to theabsorption reactor 116.

Referring to FIG. 3, a third PEP system 300 is disclosed, which has anumber of system components common with PEP 100 and PEP 200. In thealternative embodiment illustrated by FIG. 3, the third PEP system 300additionally comprises a regenerator 120 (e.g., a desorption vessel).Alternatively to the first and second PEP systems 100 and 200,respectively, in the embodiment illustrated in FIG. 3, a complexedstream 28 may be communicated from the absorption reactor 116 to theregenerator 120. A recycle stream 22 may be communicated from theregenerator 120 to the separator 108, and a regenerated absorbent stream30 may be communicated from the regenerator 120 to the absorptionreactor 116.

Various embodiments of suitable PEP systems having been disclosed,embodiments of a PEP process are now disclosed. One or more of theembodiments of a PEP process may be described with reference to one ormore of PEP system 100, PEP system 200, and/or PEP system 300. Althougha given PEP process may be described with reference to one or moreembodiments of a PEP system, such a disclosure should not be construedas so-limiting. Although the various steps of the processes disclosedherein may be disclosed or illustrated in a particular order, suchshould not be construed as limiting the performance of these processesto any particular order unless otherwise indicated.

Referring to FIG. 4, a first PEP process 400 is illustrated. PEP process400 generally comprises at block 51 purifying a feed stream, at block 52polymerizing monomers of the purified feed stream to form apolymerization product, at block 53 separating the polymerizationproduct into a polymer stream and a gas stream, at block 54 processingthe polymer stream, at block 55 separating at least one gaseouscomponent from the gas stream to form a recycle stream and a wastestream, and at block 56 combusting the waste stream.

In an embodiment, the first PEP process 400 or a portion thereof may beimplemented via the first PEP system 100 (e.g., as illustrated in FIG.1). Referring to FIGS. 1 and 4, in an embodiment the feed stream 10 maycomprise a gaseous reactant, particularly, ethylene. In an embodiment,purifying the feed stream may yield a purified stream 1 comprisingsubstantially pure monomers (e.g., ethylene monomers) as will bedescribed herein. Polymerizing monomers of the purified stream 1 mayyield the polymerization product stream 12 generally comprisingunreacted ethylene, ethane (which may be by-product ethane formed fromethylene and hydrogen) and a polymerization product (e.g.,polyethylene). Separating the polymerization product stream 12 may yieldthe polymer stream 14 (e.g., polyethylene polymer) and the gas stream 18generally comprising unreacted monomer (e.g., ethylene monomer) andvarious waste gases (e.g., ethane). Processing the polymer stream 14 mayyield the product stream 16. Separating at least one gaseous componentfrom the gas stream 18 may yield a recycle stream 22, generallycomprising unreacted ethylene monomer, and a waste gas stream 20. In anembodiment, separating the gas stream 18 comprises absorbing ethylenefrom the gas stream 18 to yield the waste gas stream 20 and thenreleasing the absorbed ethylene to form the recycle stream 22. Therecycle stream 22, comprising ethylene, may be pressurized (e.g.,returned to the separator 108 for pressurization) and re-introduced intoa PEP process (e.g., PEP process 400) as reintroduction stream 24.Combusting the waste gas stream 20 may be carried out with flare 114.

Referring to FIG. 5, a second PEP process 500 is illustrated, which hasa number of process steps common with PEP process 400. In thealternative embodiment illustrated by FIG. 5, block 55 of FIG. 4 isenhanced by at block 57 treating the gas stream to form a treated gasstream and at block 55′ separating at least one gaseous component fromthe treated gas stream to form a recycle stream and a waste stream.

In an embodiment, second PEP process 500 or a portion thereof may beimplemented via the second PEP system 200 (e.g. as illustrated in FIG.2). Alternatively to the embodiments of FIGS. 1 and 4, in the embodimentof FIGS. 2 and 5 treating the gas stream 18 may yield the treated gasstream 26. In an embodiment, treating the gas stream 18 comprisesdeoxygenating the gas stream 18. Separating at least one gaseouscomponent from the treated gas stream 26 may yield a recycle stream 22,generally comprising unreacted ethylene monomer, and a waste gas stream20.

Referring to FIG. 6, a third PEP process 600 is illustrated, which has anumber of process steps common with PEP process 500. In the alternativeembodiment illustrated by FIG. 6, block 55′ of FIG. 5 is enhanced by atblock 55″ separating at least one gaseous component from the treated gasstream to form a complexed stream and a waste gas stream and at block 58separating the complexed stream into an absorbent stream and a recyclestream.

In an embodiment, third PEP process 600 or a portion thereof may beimplemented via the third PEP system 300 (e.g. as illustrated in FIG.3). Alternatively to the embodiments of FIGS. 1 & 4 and 2 & 5, in theembodiment of FIGS. 3 and 6 separating at least one gaseous componentfrom the treated gas stream 26 may yield an unreacted monomer-absorbent(e.g., an ethylene-absorbent) complexed stream 28. In an embodiment,separating the unreacted monomer-absorbent complexed stream 28 comprisesreleasing the absorbed ethylene to form a recycle stream 22 and aregenerated absorbent stream 30.

In one or more of the embodiments disclosed herein, purifying a feedstream (e.g., at block 51) may comprise separating unwanted compoundsand elements from a feed stream comprising ethylene to form a purifiedfeed stream. In an embodiment, the feed stream may comprise ethylene andvarious other gases, such as but not limited to methane, ethane,acetylene, propylene, various other hydrocarbons having three or morecarbon atoms, or combinations thereof. In an embodiment, purifying afeed stream may comprise any suitable method or process, including thenon-limiting examples filtering, membrane screening, reacting withvarious chemicals, absorbing, adsorbing, distillation(s), orcombinations thereof.

In embodiments as illustrated by FIGS. 1-3, purifying a feed stream maycomprise routing the feed stream 10 to the purifier 102. In one or moreof the embodiments disclosed herein, the purifier 102 may comprise adevice or apparatus suitable for the purification of one or morereactant gases in a feed stream comprising a plurality of potentiallyunwanted gaseous compounds, elements, contaminants, or the like.Non-limiting examples of a suitable purifier 102 may comprise a filter,a membrane, a reactor, an absorbent, a molecular sieve, one or moredistillation columns, or combinations thereof. The purifier 102 may beconfigured to separate ethylene from a stream comprising methane,ethane, acetylene, propane, propylene, water, oxygen various othergaseous hydrocarbons, various contaminants, and/or combinations thereof.

In an embodiment, purifying a feed stream may yield a purified feed 1comprising substantially pure ethylene. In an embodiment, the purifiedfeed stream may comprise less than 25% by weight, alternatively, lessthan about 10%, alternatively, less than about 1.0% of any one or moreof nitrogen, oxygen, methane, ethane, propane, or combinations thereof.As used herein “substantially pure ethylene” refers to a fluid streamcomprising at least about 60% ethylene, alternatively, at least about70% ethylene, alternatively, at least about 80% ethylene, alternatively,at least about 90% ethylene, alternatively, at least about 95% ethylene,alternatively, at least about 99% ethylene by weight, alternatively, atleast about 99.5% ethylene by weight. In an embodiment, the feed stream1 may further comprise trace amounts of ethane, for examples, as from arecycle stream as will be discussed.

In one or more of the embodiments disclosed herein, polymerizingmonomers of the purified feed (e.g., at block 52) comprises allowing apolymerization reaction between a plurality of monomers by contacting amonomer or monomers with a catalyst system under conditions suitable forthe formation of a polymer. In an embodiment, any suitable catalystsystem may be employed. A suitable catalyst system may comprise acatalyst and, optionally, a co-catalyst and/or promoter. Nonlimitingexamples of suitable catalyst systems include Ziegler Natta catalysts,Ziegler catalysts, chromium catalysts, chromium oxide catalysts,chromocene catalysts, metallocene catalysts, nickel catalysts, orcombinations thereof. Catalyst systems suitable for use in thisdisclosure have been described, for example, in U.S. Pat. No. 7,619,047and U.S. Patent Application Publication Nos. 2007/0197374, 2009/0004417,2010/0029872, 2006/0094590, and 2010/0041842, each of which isincorporated by reference herein in its entirety.

In embodiments as illustrated by FIGS. 1-3, polymerizing monomers of thepurified feed may comprise routing the feed stream 1 to thepolymerization reactors or “reactors” 104, 106. In one or more of theembodiments disclosed herein, the reactors 104, 106 may comprise anyvessel or combination of vessels suitably configured to provide anenvironment for a chemical reaction (e.g., a contact zone) betweenmonomers (e.g., ethylene) and/or polymers (e.g., an “active” or growingpolymer chain) in the presence of a catalyst to yield a polymer (e.g., apolyethylene polymer). Although the embodiments illustrated in FIGS. 1,2, and 3, illustrate various PEP systems having two reactors in series,one of skill in the art viewing this disclosure will recognize that onereactor, alternatively, any suitable number and/or configuration ofreactors may be employed.

As used herein, the terms “polymerization reactor” or “reactor” includeany polymerization reactor capable of polymerizing olefin monomers toproduce homopolymers or copolymers. Such homopolymers and copolymers arereferred to as resins or polymers. The various types of reactors includethose that may be referred to as batch, slurry, gas-phase, solution,high pressure, tubular or autoclave reactors. Gas phase reactors maycomprise fluidized bed reactors or staged horizontal reactors. Slurryreactors may comprise vertical or horizontal loops. High pressurereactors may comprise autoclave or tubular reactors. Reactor types caninclude batch or continuous processes. Continuous processes could useintermittent or continuous product discharge. Processes may also includepartial or full direct recycle of un-reacted monomer, un-reactedcomonomer, and/or diluent.

Polymerization reactor systems of the present invention may comprise onetype of reactor in a system or multiple reactors of the same ordifferent type. Production of polymers in multiple reactors may includeseveral stages in at least two separate polymerization reactorsinterconnected by a transfer device making it possible to transfer thepolymers resulting from the first polymerization reactor (e.g., reactor104) into the second reactor (e.g., reactor 106). The desiredpolymerization conditions in one of the reactors may be different fromthe operating conditions of the other reactors. Alternatively,polymerization in multiple reactors may include the manual transfer ofpolymer from one reactor to subsequent reactors for continuedpolymerization. Multiple reactor systems may include any combinationincluding, but not limited to, multiple loop reactors, multiple gasreactors, a combination of loop and gas reactors, multiple high pressurereactors or a combination of high pressure with loop and/or gasreactors. The multiple reactors may be operated in series or inparallel.

According to one aspect of the invention, the polymerization reactorsystem may comprise at least one loop slurry reactor comprising verticalor horizontal loops. Monomer, diluent, catalyst and optionally anycomonomer may be continuously fed to a loop reactor where polymerizationoccurs. Generally, continuous processes may comprise the continuousintroduction of a monomer, a catalyst, and a diluent into apolymerization reactor and the continuous removal from this reactor of asuspension comprising polymer particles and the diluent. Reactoreffluent may be flashed to remove the solid polymer from the liquidsthat comprise the diluent, monomer and/or comonomer. Varioustechnologies may be used for this separation step including but notlimited to, flashing that may include any combination of heat additionand pressure reduction; separation by cyclonic action in either acyclone or hydrocyclone; or separation by centrifugation.

A typical slurry polymerization process (also known as the particle formprocess), is disclosed, for example, in U.S. Pat. Nos. 3,248,179,4,501,885, 5,565,175, 5,575,979, 6,239,235, 6,262,191 and 6,833,415,each of which is incorporated by reference in its entirety herein.

Suitable diluents used in slurry polymerization include, but are notlimited to, the monomer being polymerized and hydrocarbons that areliquids under reaction conditions. Examples of suitable diluentsinclude, but are not limited to, hydrocarbons such as propane,cyclohexane, isobutane, n-butane, n-pentane, isopentane, neopentane, andn-hexane. Some loop polymerization reactions can occur under bulkconditions where no diluent is used. An example is polymerization ofpropylene monomer as disclosed in U.S. Pat. No. 5,455,314, which isincorporated by reference herein in its entirety.

According to yet another aspect of this invention, the polymerizationreactor may comprise at least one gas phase reactor. Such systems mayemploy a continuous recycle stream containing one or more monomerscontinuously cycled through a fluidized bed in the presence of thecatalyst under polymerization conditions. A recycle stream may bewithdrawn from the fluidized bed and recycled back into the reactor.Simultaneously, polymer product may be withdrawn from the reactor andnew or fresh monomer may be added to replace the polymerized monomer.Such gas phase reactors may comprise a process for multi-step gas-phasepolymerization of olefins, in which olefins are polymerized in thegaseous phase in at least two independent gas-phase polymerization zoneswhile feeding a catalyst-containing polymer formed in a firstpolymerization zone to a second polymerization zone. One type of gasphase reactor is disclosed in U.S. Pat. Nos. 5,352,749, 4588,790 and5,436,304, each of which is incorporated by reference in its entiretyherein.

According to still another aspect of the invention, a high pressurepolymerization reactor may comprise a tubular reactor or an autoclavereactor. Tubular reactors may have several zones where fresh monomer,initiators, or catalysts are added. Monomer may be entrained in an inertgaseous stream and introduced at one zone of the reactor. Initiators,catalysts, and/or catalyst components may be entrained in a gaseousstream and introduced at another zone of the reactor. The gas streamsmay be intermixed for polymerization. Heat and pressure may be employedappropriately to obtain optimal polymerization reaction conditions.

According to yet another aspect of the invention, the polymerizationreactor may comprise a solution polymerization reactor wherein themonomer is contacted with the catalyst composition by suitable stirringor other means. A carrier comprising an inert organic diluent or excessmonomer may be employed. If desired, the monomer may be brought in thevapor phase into contact with the catalytic reaction product, in thepresence or absence of liquid material. The polymerization zone ismaintained at temperatures and pressures that will result in theformation of a solution of the polymer in a reaction medium. Agitationmay be employed to obtain better temperature control and to maintainuniform polymerization mixtures throughout the polymerization zone.Adequate means are utilized for dissipating the exothermic heat ofpolymerization.

Polymerization reactors suitable for the present invention may furthercomprise any combination of at least one raw material feed system, atleast one feed system for catalyst or catalyst components, and/or atleast one polymer recovery system. Suitable reactor systems for thepresent invention may further comprise systems for feedstockpurification, catalyst storage and preparation, extrusion, reactorcooling, polymer recovery, fractionation, recycle, storage, loadout,laboratory analysis, and process control.

Conditions that are controlled for polymerization efficiency and toprovide resin properties include temperature, pressure and theconcentrations of various reactants. Polymerization temperature canaffect catalyst productivity, polymer molecular weight and molecularweight distribution. Suitable polymerization temperature may be anytemperature below the de-polymerization temperature according to theGibbs Free energy equation. Typically this includes from about 60° C. toabout 280° C., for example, and from about 70° C. to about 110° C.,depending upon the type of polymerization reactor.

Suitable pressures will also vary according to the reactor andpolymerization type. The pressure for liquid phase polymerizations in aloop reactor is typically less than 1000 psig. Pressure for gas phasepolymerization is usually at about 200-500 psig. High pressurepolymerization in tubular or autoclave reactors is generally run atabout 20,000 to 75,000 psig. Polymerization reactors can also beoperated in a supercritical region occurring at generally highertemperatures and pressures. Operation above the critical point of apressure/temperature diagram (supercritical phase) may offer advantages.In an embodiment, polymerization may occur in an environment having asuitable combination of temperature and pressure. For example,polymerization may occur at a pressure in a range from about 550 psi toabout 650 psi, alternatively, about 600 psi to about 625 psi and atemperature in a range from about 170° F. to about 230° F.,alternatively, from about 195° F. to about 220° F.

The concentration of various reactants can be controlled to produceresins with certain physical and mechanical properties. The proposedend-use product that will be formed by the resin and the method offorming that product determines the desired resin properties. Mechanicalproperties include tensile, flexural, impact, creep, stress relaxationand hardness tests. Physical properties include density, molecularweight, molecular weight distribution, melting temperature, glasstransition temperature, temperature melt of crystallization, density,stereoregularity, crack growth, long chain branching and rheologicalmeasurements.

The concentrations and/or partial pressures of monomer, co-monomer,hydrogen, co-catalyst, modifiers, and electron donors are important inproducing these resin properties. Comonomer may be used to controlproduct density. Hydrogen may be used to control product molecularweight. Co-catalysts can be used to alkylate, scavenge poisons andcontrol molecular weight. Modifiers can be used to control productproperties and electron donors affect stereoregularity, the molecularweight distribution, or molecular weight. In addition, the concentrationof poisons is minimized because poisons impact the reactions and productproperties.

In an embodiment, polymerizing monomers of the purified feed maycomprise introducing a suitable catalyst system into the first and/orsecond reactor 104, 106, respectively, so as to form a slurry.Alternatively, a suitable catalyst system may reside in the first and/orsecond reactor 104, 106, respectively.

As explained above, polymerizing monomers of the purified feed maycomprise selectively manipulating one or more polymerization reactionconditions to yield a given polymer product, to yield a polymer producthaving one or more desirable properties, to achieve a desiredefficiency, to achieve a desired yield, the like, or combinationsthereof. Non-limiting examples of such parameters include temperature,pressure, type and/or quantity of catalyst or co-catalyst, and theconcentrations and/or partial pressures of various reactants. In anembodiment, polymerizing monomers of the purified feed 52 may compriseadjusting one or more polymerization reaction conditions.

In an embodiment, polymerizing monomers of the purified feed maycomprise maintaining a suitable temperature, pressure, and/or partialpressure(s) during the polymerization reaction, alternatively, cyclingbetween a series of suitable temperatures, pressures, and/or partialspressure(s) during the polymerization reaction.

In an embodiment, polymerizing monomers of the purified feed maycomprise circulating, flowing, cycling, mixing, agitating, orcombinations thereof, the monomers, catalyst system, and/or the slurrywithin and/or between the reactors 104, 106. In an embodiment where themonomers, catalyst system, and/or slurry are circulated, circulation maybe at a velocity (e.g., fluid velocity) of from about 1 m/s to about 30m/s, alternatively, from about 2 m/s to about 17 m/s, alternatively,from about 3 m/s to about 15 m/s.

In an embodiment, polymerizing monomers of the purified feed maycomprise configuring reactors 104, 106 to yield a multimodal (e.g., abimodal) polymer (e.g., polyethylene). For example, the resultantpolymer may comprise both a relatively high molecular weight, lowdensity (HMWLD) polyethylene polymer and a relatively low molecularweight, high density (LMWHD) polyethylene polymer. For example, varioustypes of suitable polymers may be characterized as having a variousdensities. For example, a Type I may be characterized as having adensity in a range of from about 0.910 g/cm³ to about 0.925 g/cm³,alternatively, a Type II may be characterized as having a density fromabout 0.926 g/cm³ to about 0.940 g/cm³, alternatively, a Type III may becharacterized as having a density from about 0.941 g/cm³ to about 0.959g/cm³, alternatively, a Type IV may be characterized as having a densityof greater than about 0.960 g/cm³.

In the embodiments illustrated in FIGS. 1-3, polymerizing monomers ofthe purified feed may yield a polymerization product stream 12. Such apolymerization product stream 12 may generally comprise various solids,semi-solids, volatile and nonvolatile liquids, gases and combinationsthereof. In an embodiment, the polymerization product stream 12 maycomprise hydrogen, nitrogen, methane, ethylene, ethane, propylene,propane, butane, isobutane, pentane, hexane, hexene-1 and heavierhydrocarbons. In an embodiment, ethylene may be present in a range offrom about 0.1% to about 15%, alternatively, from about 1.5% to about5%, alternatively, about 2% to about 4% by weight. Ethane may be presentin a range of from about 0.001% to about 4%, alternatively, from about0.2% to about 0.5% by weight. Isobutane may be present in a range fromabout 80% to about 98%, alternatively, from about 92% to about 96%,alternatively, about 95% by weight.

The solids and/or liquids may comprise a polymer product (e.g., apolyethylene polymer), often referred to at this stage of the PEPprocess as “polymer fluff.” The gases may comprise unreacted, gaseousreactant monomers (e.g., unreacted ethylene monomers), gaseous wasteproducts, and/or gaseous contaminants.

In one or more of the embodiments disclosed herein, separating thepolymerization product into a polymer stream and a gas stream (e.g., atblock 53) may generally comprise removing any gases from liquids and/orsolids (e.g., the polymer fluff) by any suitable process.

In embodiments as illustrated by FIGS. 1-3, separating thepolymerization product into a polymer stream and a gas stream maycomprise routing the polymerization product steam 12 to the separator108. In one or more of the embodiments disclosed herein, the separator108 may be configured to separate a stream (e.g., polymerization productcomprising polyethylene) into gases, liquids, solids, or combinationsthereof. The reaction product may comprise unreacted, gaseous monomers(e.g., unreacted ethylene monomers), gaseous waste products, and/orgaseous contaminants. As used herein, an “unreacted monomer,” forexample, ethylene, refers to a monomer that was introduced into apolymerization reactor during a polymerization reaction but was notincorporated into a polymer.

In an embodiment, the separator 108 may comprise a vapor-liquidseparator. Suitable examples of such a separator may include adistillation column, a flash tank, a filter, a membrane, a reactor, anabsorbent, an adsorbent, a molecular sieve, or combinations thereof. Inan embodiment, the separator comprises a flash tank. Not seeking to bebound by theory, such a flash tank may comprise a vessel configured tovaporize and/or remove low vapor pressure components from a hightemperature and/or high pressure fluid. The separator 108 may beconfigured such that an incoming stream may be separated into a liquidstream (e.g., a condensate stream) and a gas (e.g., vapor) stream. Theliquid or condensate stream may comprise a reaction product (e.g.,polyethylene), often referred to as “polymer fluff.” The gas or vaporstream may comprise volatile solvents, gaseous, unreacted monomers,waste gases (secondary reaction products, such as contaminants and thelike), or combinations thereof. The separator may be configured suchthat the feed stream is flashed by heat, pressure reduction, or bothsuch that the enthalpy of the stream is increased. This may beaccomplished via a heater, a flashline heater, various other operationscommonly known in the art, or combinations thereof. For example, a flashline heater comprising a double pipe may exchange heat by hot water orsteam. Such a flashline heater may increase the temperature of thestream while reducing its pressure.

In an embodiment, separating the polymerization product into a polymerstream and a gas stream 53 may comprise distilling, vaporizing,flashing, filtering, membrane screening, absorbing, adsorbing, orcombinations thereof, the polymerization product. In the embodimentsillustrated in FIGS. 1-3, separating the polymerization product into apolymer stream and a gas stream yields a gas stream 18 and a polymerstream 14. In an embodiment, the gas stream may comprise hydrogen,nitrogen, methane, ethylene, ethane, propylene, propane, butane,isobutane, pentane, hexane, hexene-1 and heavier hydrocarbons. In anembodiment, ethylene may be present in a range of from about 0.1% toabout 15%, alternatively, from about 1.5% to about 5%, alternatively,about 2% to about 4% by weight. Ethane may be present in a range of fromabout 0.001% to about 4%, alternatively, from about 0.2% to about 0.5%by weight. Isobutane may be present in a range from about 80% to about98%, alternatively, from about 92% to about 96%, alternatively, about95% by weight.

In one or more one or more of the embodiments disclosed herein,processing the polymer stream (e.g., at block 54) comprises any suitableprocess or series of processes configured to produce a polymer productas may be suitable for commercial or industrial usage, storage,transportation, further processing, or combinations thereof.

In embodiments as illustrated by FIGS. 1-3, processing the polymerstream may comprise routing the polymer stream 14 to the processor 110.The processor 110 may be configured for the performance of a suitableprocessing means, nonlimiting examples of which include cooling,injection molding, melting, pelletizing, blow molding, extrusionmolding, rotational molding, thermoforming, cast molding, the like, orcombinations thereof. Various additives and modifiers may be added tothe polymer to provide better processing during manufacturing and fordesired properties in the end product. Nonlimiting examples of suchadditives may include surface modifiers such as slip agents, antiblocks,tackifiers; antioxidants such as primary and secondary antioxidants;pigments; processing aids such as waxes/oils and fluoroelastomers; andspecial additives such as fire retardants, antistats, scavengers,absorbers, odor enhancers, and degradation agents.

In an embodiment, the processor 110 may be configured to form a suitablepolymer product. Nonlimiting examples of suitable polymer products asmay result from such processing include films, powders, pellets, resins,liquids, or any other suitable form as will be appreciated by those ofskill in the art. Such a suitable output may be for use in, forexamples, one or more of various consumer or industrial products. Forexample, the polymer product may be utilized any one or more of variousarticles, including, but not limited to, bottles, drums, toys, householdcontainers, utensils, film products, drums, fuel tanks, pipes,geomembranes, and liners. In a particular embodiment, the processor isconfigured to form pellets for transportation to a consumer productmanufacturer. For example, in the embodiments illustrated in FIGS. 1-3,processing the polymer stream yields a polymer product 16 (e.g.,pelletized polyethylene).

In one or more one or more of the embodiments disclosed herein, treatingthe gas stream (e.g., at block 57) comprises any suitable process orreaction for removing oxygen, oxygenated compounds, oxidizing compounds,or combinations thereof (cumulatively referred to herein as “oxygen”)from the gas stream. Suitable processes or reactions will be appreciatedby those of skill in the art viewing this disclosure. Nonlimitingexamples of suitable processes for removing oxygen include variouscatalyzed reactions, contacting with a chemical species known to reactwith oxygen, filtering, absorbing, adsorbing, heating, cooling, orcombinations thereof.

In embodiments as illustrated by FIGS. 2-3, treating the gas stream maycomprise routing the gas stream 18 to the deoxygenator 118. In one ormore one or more of the embodiments disclosed herein, the deoxygenator118 may comprise a device or apparatus configured for the removaloxygen, from a gas stream. Nonlimiting examples of a suitabledeoxygenator include various reactors (e.g., a fluidized bed reactor ora fixed bed), a filter, or combinations thereof. A suitable deoxygenator118 may be configured to reduce, prevent, or exclude compounds and/orelements (e.g., oxygen) that may have the effect of poisoning anabsorption solvent from reaching the absorption reactor.

In the embodiments illustrated by FIGS. 2-3, treating the gas streamyields a treated gas stream 26 being substantially free of oxygen. Asused herein “substantially free of oxygen” refers to a fluid streamcomprising no more than least about 5% oxygen, alternatively, no morethan about 1% oxygen, alternatively, no more than about 0.1% oxygen,alternatively, no more than about 0.01% oxygen by weight.

In one or more one or more of the embodiments disclosed herein,separating at least one gaseous component from the gas stream and/or thetreated gas stream, collectively referred to as a gas stream, (e.g., atblock 55, 55′, or 55″) generally comprises any suitable method ofselectively separating at least a first chemical component or compoundfrom a stream comprising the first chemical component or compound andone or more other chemical components, compounds, or the like. Invarious embodiments, the gaseous component separated from the gas streammay comprise one or more hydrocarbons. Nonlimiting examples of suchhydrocarbons include alkanes (e.g., butane, particularly, isobutane) andalkenes or olefin monomers (e.g., ethylene). In an embodiment, thegaseous component separated from the gas stream may comprise anunreacted hydrocarbon monomer, e.g., ethylene. In an embodiment, thegaseous component separated from the gas stream may comprise anunreacted hydrocarbon monomer, e.g., ethylene, alone or in combinationwith other hydrocarbons, e.g., isobutane. In an embodiment, the gaseouscomponent separated from the gas stream may comprise ethylene, alone orin combination with isobutane. In an embodiment, capturing isobutane mayresult in a savings of the cost of the captured isobutane and reduce thepresence of isobutene in flare emissions. Nonlimiting examples ofsuitable separating means include distilling, vaporizing, flashing,filtering, membrane screening, absorbing, adsorbing, molecular weightexclusion, size exclusion, polarity-based separation, or combinationsthereof.

In an embodiment as illustrated by FIGS. 1-3, separating at least onegaseous component from the gas stream (e.g., gas stream 18 of FIG. 1 ortreated gas stream 26 of FIGS. 2-3) may comprise routing the gas streamto the absorption reactor 116. In one or more one or more of theembodiments disclosed herein, the absorption reactor 116 may comprise areactor configured to selectively absorb at least a first chemicalcomponent or compound from a stream comprising the first chemicalcomponent or compound and one or more other chemical components,compounds, or the like. Non-limiting examples of suitable absorptionreactors include an absorption (distillation) tower, a sparger tank, anagitation reactor, one or more compressors, one or more recycle pumps,or combinations thereof. For examples, in an embodiment the absorptionreactor may be configured to dissipate a gas within a liquid (e.g., bybubbling the gas through the liquid). For example, a suitable absorptionreactor is illustrated in the Gas Processors Association, “EngineeringData Book” 10^(th) ed. at FIG. 19-46. The absorption reactor 116 may becapable of selectively inducing thermal and/or pressure fluctuations,variations, or cycles. In an embodiment, the absorption reactor 116 maybe configured to selectively absorb and/or induce the absorption of anunreacted ethylene monomer from a composition comprising various othergases (e.g., ethane). In another embodiment, the absorption reactor 116may be configured to selectively absorb and/or induce the absorption ofbutane, particularly, isobutane, from a composition comprising variousother gases. In still another embodiment, the absorption reactor 116 maybe configured to selectively absorb both unreacted ethylene and butane,particularly, isobutane, from a composition comprising various othergases (e.g., ethane).

In an embodiment where the absorption reactor 116 comprises a solventreactor, the absorption reactor may comprise a suitable absorptionsolvent system, as will be disclosed herein. Such an absorption reactor116 may be configured to retain the absorption solvent system. Forexample, the absorption solvent system may retained within the reactoras a liquid, as a fixed bed, or as a fluidized bed.

In an embodiment, a suitable absorption solvent system may be capable ofreversibly complexing with the ethylene and/or isobutane. Such anabsorption solvent system may generally comprise a metallic salt and asolvent. In an embodiment, an absorption solvent system may becharacterized as having a selectivity of ethylene to ethane whereethylene and ethane are present at the same partial pressure of about40:1 at approximately 14 psi, about 12:1 at approximately 20 psi, about6:1 at approximately 40 psi, and about 3:1 at approximately 180 psipartial pressure. In an embodiment, the solvent system may be furthercharacterized as having a high contaminant tolerance and as exhibitinghigh stability at increased and/or fluctuating temperatures and/orpressures, or combinations thereof.

In an embodiment, the metallic salt may comprise a salt of one or moretransition metals and a weakly-ionic halogen. Non-limiting examples ofsuitable transition metals include silver, gold, copper, platinum,palladium, or nickel. Non-limiting example of suitable weakly-ionichalogens include chlorine and bromine. In an embodiment, a suitabletransition metal salt may be characterized as having a high specificityfor olefins. Non-limiting examples of suitable transition metal-halogensalts include silver chloride (AgCl) and copper chloride (CuCl). In aparticular embodiment, the salt employed in the absorption solventsystem comprises CuCl. Not seeking to be bound by theory, such ametallic salt may interact with the double carbon bonds of olefins.

In an embodiment, the solvent comprises an amine or an amine complex.Non-limiting examples of solvent amines include pyridine, benzylamine,and aniline. For examples, the amine may comprise an aniline(phenylamine, aminobenzene); alternatively, aniline combined withdimethyleformamide (DMF), and in embodiments, aniline andN-methylpyrrolidone (NMP).

In an embodiment, the solvent may be characterized as aprotic, that is,as not including a dissociable hydrogen atom. Without limitation bytheory, a dissociable hydrogen solvent may result in the hydrogenationof the double bond between carbons in an olefin such as ethylene.Further, the solvent may be characterized as polar, as having a slightpolarity, or as having unidirectional, electric charge. Not seeking tobe bound by theory, a polar solvent may interact with and at leastpartially solubilize the salt.

In an embodiment, the solvent may be characterized as a liquid producedindustrially in relatively high volumes, having a relatively low cost,being easily transportable, or combinations thereof. The solvent may befurther characterized as capable of retaining a complexed olefin-metalsalt or retaining a weakly ionic metal salt despite fluctuations intemperature and/or pressure.

In an embodiment, the absorption solvent system may comprise copperchloride, aniline, and dimethylformamide (CuCl/aniline/DMF). In analternative embodiment, the absorption solvent system may comprisecopper chloride, aniline, and N-methylpyrrolidone (CuCl/aniline/NMP). Inethylene absorption applications, a CuCl/aniline/NMP solvent system maybe characterized as having increased volatile stability at lowerpressures and higher temperatures.

In an embodiment, the absorption reactor 116 may be configured toprovide or maintain a suitable pressure during operation. Such asuitable pressure may be in a range of from about 5 psig to about 500psig, alternatively, from about 50 psig to about 450 psig,alternatively, from about 75 psig to about 400 psig. In an additionalembodiment, the absorption reactor 116 may be configured to provide ormaintain a suitable partial pressure of ethylene during operation. Sucha suitable ethylene partial pressure may be in a range of from about 1psia to about 400 psia, alternatively, from about 30 psia to about 200psia, alternatively, from about 50 psia to about 250 psia. Not intendingto be bound by theory, pressurizing the absorption reactor 116 mayfacilitate absorption of ethylene and/or the formation of a complex ofethylene and the absorption solvent system (e.g., the CuCl/aniline/NMPsystem). Also, without limitation by theory, the selectivity of theabsorption solvent system for ethylene may increase with a decrease inthe pressure of the absorption reactor.

In an embodiment, the absorption reactor may be configured for theremoval of unabsorbed gases therefrom. In an embodiment, the absorptionreactor 116 may be capable of inducing thermal fluctuations, forexample, such that unabsorbed gases may be flashed from the absorptionreactor 116. Such an absorption reactor 116 may be configured to provideor maintain a suitable temperature. Such a suitable temperature may bein a range of from about 0° C. to about 250° C., alternatively, fromabout 50° C. to about 200° C., alternatively, from about 75° C. to about150° C. to facilitate removal of the unabsorbed gases.

In an embodiment, the absorption reactor 116 may be configured to inducethe release of the gas absorbed or complexed by the absorption solventtherefrom (e.g., absorbed and/or complexed ethylene and/or isobutane).Not intending to be bound by theory, inducing the release of theabsorbed or complexed gas may comprise altering the reaction kinetics orthe gas-solvent equilibrium of the absorption solvent system, thetemperature of the absorption reactor 116, the pressure of theabsorption reactor 116, the partial pressure of the absorbed gas, orcombinations thereof. In such an embodiment, the absorption reactor 116may comprise controls, thermal conduits, electric conduits, compressors,vacuums, the like, or combinations thereof configured to alter thereaction kinetics, the gas-solvent equilibrium, the temperature of theabsorption reactor 116, the pressure of the absorption reactor 116, orcombinations thereof.

In an embodiment, the absorption reactor 116 may be configured toevacuate gases (e.g., a previously absorbed and then released gas, suchas ethylene) and/or to facilitate the release of the absorbed gas via apressure differential. The absorption reactor 116 may be configured toprovide or maintain a suitable partial pressure. Such a suitable partialpressure may be in a range of from about 0.1 psig to about 40 psig,alternatively, from about 5 psig to about 30 psig, alternatively, fromabout 5 psig to about 15 psig. In an embodiment, the absorption reactor116 may be configured to provide or maintain an ethylene partialpressure in a range of from about 0 psia to about 5 psia.

In an embodiment, the absorption reactor 116 may be configured for batchand/or continuous processes. For example, in an embodiment, a PEP systemmay comprise two or more absorption reactors (e.g., such as absorptionreactor 116), each of which may be configured for batch operation. Forexample, by employing two or more absorption reactors, such a system maybe configured to allow for continuous operation by running a first batchin the first absorption reactor while a second batch is prepared in thesecond absorption reactor. As such, by cycling between two or moresuitable reactors, a system may operate continuously.

In an embodiment, separating at least one gaseous component from the gasstream comprises selectively absorbing the at least one gaseouscomponent from a gas stream. In such an embodiment, absorbing the atleast one gaseous component from the gas stream generally comprisescontacting the gas stream with a suitable absorbent, allowing the atleast one component to be absorbed by the absorbent, and, optionally,removing a waste stream comprising unabsorbed gases. In an additionalembodiment, separating at least one gaseous component from the gasstream may comprise liberating the absorbed gaseous component from theabsorbent (e.g., via regenerator 120). In an alternative embodiment, theabsorbed gaseous component and absorbent may be removed for furtherprocessing.

In an embodiment, contacting the gas stream with the absorbent (e.g., anabsorption solvent system) may comprise any suitable means of ensuringsufficient contact between the gas stream and the absorbent. Nonlimitingexamples of suitable means by which to provide sufficient contactbetween the gas stream and the absorbent include the use of variousreactor systems, such as those disclosed above (e.g., an absorptioncolumn or sparged or mixed tank). Not intending to limited by theory, asuitable reactor system may ensure contact between a two or moregaseous, liquid, and or solid compositions by agitating or mixing thetwo components in the presence of each other, circulating, dispersing,or diffusing a first composition through or within a second composition,or various other techniques known to those of skill in the art. In anembodiment, the gas stream and the absorbent may be brought into contactin a suitable ratio. Such a suitable ratio of gas stream to absorbentmay be in a range of from about 1,000 lb/hr: 1000 gpm to about 2,500lb/hr: 25 gpm, alternatively, from about 1000 lb/hr: 250 gpm to about2500 lb/hr: 100 gpm, alternatively, about 1875 lbs/hr: 250 gpm.

In an embodiment, allowing the at least one component to be absorbed bythe absorbent may comprise allowing the at least one component to becomereversibly bound, linked, bonded or combinations thereof to theabsorbent or a portion thereof, for example, via the formation ofvarious links, bonds, attractions, complexes, or combinations thereof.For example, in an embodiment where the absorbent comprises anabsorption solvent system (e.g., a CuCl/aniline/DMF solvent system or aCuCl/aniline/NMP solvent system), allowing absorption of the at leastone component may comprise allowing a complex to form between theabsorbent and the at least one component, referred to as an absorbedcomponent complex (e.g., an absorbed ethylene complex).

Allowing absorption of the at least one component may further compriseproviding and/or maintaining a suitable pressure of the environment inwhich the gas stream and absorbent are brought into contact, providingand/or maintaining a suitable partial pressure of a gas, providingand/or maintaining a suitable temperature in the environment in whichthe gas stream and absorbent are brought into contact, catalyzing theabsorption, or combinations thereof. Not intending to be bound bytheory, the absorption of the at least one component by the absorbentmay be improved at a suitable temperature and/or pressure.

In an embodiment, separating at least one gaseous component from the gasstream comprises removing a waste stream. In an embodiment, theremaining unabsorbed gas stream components form the waste stream. In anembodiment where the absorbed component comprises ethylene and theabsorbent comprises a CuCl/aniline/DMF or a CuCl/aniline/NMP solventsystem, such a waste stream may comprise methane, ethane, acetylene,propylene, various other hydrocarbons, volatile contaminants, orcombinations thereof. Further, such a waste stream may be substantiallyfree of ethylene monomers. As used herein, “substantially free ofunreacted ethylene monomers” means that the waste gases comprise lessthan 50% unreacted ethylene monomers, alternatively, less than 10%unreacted ethylene monomers, alternatively, less than 1.0% unreactedethylene monomers, alternatively, less than 0.1 unreacted ethylenemonomers, alternatively, less than 0.01% unreacted ethylene monomers byweight.

In an embodiment, removing the waste stream comprises cooling the wastestream, reducing or increasing the waste stream pressure such that thewaste stream flows to the flare 114. For example, in an embodiment, thewaste stream may be “swept away” by conveying a suitable sweep gas(e.g., an inert or unreactive gas, as disclosed above) through thevessel containing the waste gas (e.g., the absorption reactor 116) at asufficient pressure, at velocity, or combinations thereof to expel thewaste gases therefrom. For example, in the embodiments illustrated byFIGS. 1-3, separating at least one gaseous component from the gas streamyields a waste gas stream 20 being substantially free of unreactedethylene monomers, alternatively, a waste gas stream having a reducedconcentration of unreacted ethylene monomers. For example, the waste gasstream may comprise less than about 30%, alternatively, less than about25%, alternatively, less than about 20%, alternatively, less than about15%, alternatively, less than about 10% unreacted ethylene monomers byweight. In an additional embodiment, the ethylene may be decreased by apercentage of the ethylene present in the gas stream prior to separatingat least one gaseous component therefrom. For example, the waste gasstream may comprise less than about 40%, alternatively, less than about30%, alternatively, less than about 20% by weight of the unreactedethylene monomers present in the gas stream prior to separation.

In an embodiment, separating at least one gaseous component from the gasstream may further comprise liberating the absorbed gaseous componentfrom the absorbent (e.g., in situ within absorption reactor 116 and/orin another vessel such as regenerator 120). In an embodiment, theabsorbed gaseous component may be liberated from the absorbent before orafter the waste gas has been removed. Liberating the absorbed gaseouscomponent from the absorbent generally comprises any suitable means ofreversing the various links, bonds, attractions, complexes, orcombinations thereof by which the at least one gaseous component isbound, linked, bonded or combinations thereof to the absorbent or aportion thereof. Nonlimiting examples of a suitable means by which toliberate the absorbed gaseous component include altering absorptionkinetics or the absorption equilibrium of the absorbent; heating, ordepressurizing the absorbent; altering the partial pressure of theabsorbed gas, or combinations thereof. For example, in an embodiment,liberating the absorbed gaseous component may comprise depressurizingthe solution comprising the complexed ethylene to a suitable partialpressure.

In an embodiment, liberating the absorbed gas yields a recycle streamcomprising unreacted monomers which may be returned to the separator 108for pressurization (e.g., via one or more compressors located at theseparator 108). For example, in the embodiments illustrated by FIGS.1-3, liberating the absorbed gas yields a recycle stream 22 which may bereturned to the separator 108. Pressurizing the recycle stream 22 mayyield a reintroduction stream 24 which may be reintroduced into orreused in a PEP process. For example, in the embodiments illustrated byFIGS. 1-3, a reintroduction stream 24 is introduced into the purifier102. In an alternative embodiment, a recycle stream (such as recyclestream 22) may be pressurized and/or reintroduced into a PEP processwithout being returned to the separator 108. In an embodiment, therecycle stream 22 may comprise substantially pure ethylene;alternatively, the recycle stream 22 may comprise ethylene and butane,particularly, isobutane. In an embodiment, the gas stream may comprisemay comprise nitrogen, ethylene, ethane, and/or isobutene. Ethylene maybe present in a range of from about 65% to about 99%, alternatively,from about 70% to about 90%, alternatively, about 75% to about 85% byweight. Ethane may be present in a range of from about 1% to about 20%,alternatively, from about 5% to about 15%, alternatively, from about7.5% to about 12.5% by weight. Isobutane may be present in a range offrom about 1% to about 20%, alternatively, from about 5% to about 15%,alternatively, from about 7.5% to about 12.5% by weight.

In an alternative embodiment, separating at least one gaseous componentfrom the gas stream may further comprise removing the solutioncomprising the absorbed component complex (e.g., the absorbed ethylenecomplex) for further processing. For example, in the embodimentillustrated by FIG. 3, separating at least one gaseous component fromthe gas stream may yield complexed stream 28, as will be discussed ingreater detail below. In an embodiment, the complexed stream 28 maycomprise may comprise ethylene, ethane, and/or isobutane. Ethylene maybe present in a range of from about 0.1% to about 10%, alternatively,from about 0.4% to about 5%, alternatively, from about 0.5% to about2.5% by weight. Ethane may be present in a range of from about 0.1% toabout 1%, alternatively, from about 0.2% to about 0.5% by weight.Isobutane may be present in a range of from about 0.1% to about 1%,alternatively, from about 0.2% to about 0.5% by weight.

In one or more one or more of the embodiments disclosed herein,separating a complexed stream into a recycle stream and an absorbentstream (e.g., at block 58) comprises liberating the absorbed gaseouscomponent from the absorbent.

In the embodiment illustrated by FIG. 3, separating a complexed streaminto a recycle stream and an absorbent stream may comprise routing thecomplexed stream 28 to the regenerator 120. In one or more one or moreof the embodiments disclosed herein, a regenerator 120 may comprise adevice or apparatus configured to recover, regenerate, recycle, and/orpurify an absorption solvent and/or to liberate an absorbed gas.Non-limiting examples of a suitable regenerator include a flash reactor,a depressurization reactor, a solvent regeneration reactor, orcombinations thereof. In an embodiment, regenerator 120 may beconfigured to operate on the basis of a pressure differential. In suchan embodiment, the regenerator 120 may be configured to provide ormaintain a suitable internal pressure. Such a suitable internal pressuremay be in a range of from about 0.1 psia to about 150 psig,alternatively, from about 5 psig to about 30 psig, alternatively, fromabout 5 psig to about 15 psig. In an embodiment, the regenerator 120 maybe configured to provide or maintain a suitable partial pressure. Such asuitable partial pressure may be in a range of from about 0 psia toabout 50 psia. In an embodiment, regenerator 120 may be configured tooperate on the basis of an elevated temperature. Such an regenerator 120may be configured to provide or maintain a suitable temperature. Such asuitable temperature may be in a range of from about 0° C. to about 250°C., alternatively, from about 50° C. to about 80° C., alternatively,from about 60° C. to about 70° C. to vaporize and/or release an absorbedcompound (e.g., ethylene and/or isobutane) from the absorption solvent.

In an embodiment, the regenerator 120 may be configured for batch and/orcontinuous processes. For example, in an embodiment, a PEP system maycomprise two or more absorption regenerators (e.g., such as regenerator120), each of which may be configured for batch operation. As explainedabove, by employing two or more absorption reactors, such a system mayoperate to regenerate the absorbent continuously.

As explained above, liberating the absorbed gaseous component from theabsorbent generally comprises any suitable means reversing the variouslinks, bonds, attractions, complexes, or combinations thereof by whichthe at least one gaseous component is bound, linked, bonded orcombinations thereof to the absorbent or a portion thereof. Variousprocesses for liberating an absorbed gaseous component were disclosedabove with respect to the step of separating at least one gaseouscomponent from the gas stream.

In an embodiment, separating a complexed stream into a recycle streamand an absorbent stream may yield a regenerated absorbent steam whichmay be reused in an absorption reaction and a recycle stream comprisingunreacted monomers which may be reintroduced into or reused in a PEPprocess. For example, in the embodiment illustrated by FIG. 3,separating a complexed stream into a recycle stream and an absorbentstream 58 yields a recycle stream 22 which may be returned to thepurifier 102 and a regenerated absorbent stream 30 which may be returnedto the absorption reactor 116.

In one or more one or more of the embodiments disclosed herein,combusting waste gas stream (e.g., at block 56) may generally compriseburning or incinerating the gases of the waste gas stream 20.

In embodiments as illustrated by FIGS. 1-3, combusting waste gas streammay comprise routing the waste gas stream 20 to the flare 114. In one ormore one or more of the embodiments disclosed herein, the flare 114 maycomprise a combustion device or apparatus. Nonlimiting examples of asuitable flare include a torch, incinerator, the like, or combinationsthereof. A flare may suitably comprise one or more controllable nozzles,an ignition source, a bypass valve, a pressure relief valve, orcombinations thereof. Flare 114 may be configured to provide anenvironment for the combustion of various waste products, for example,atomic gases (e.g. nitrogen, oxygen), oxides (e.g. carbon monoxide,oxides of nitrogen or sulfur), various unwanted gaseous products, orcombinations thereof. In an embodiment, the flare 114 may additionallycomprise a device or apparatus configured to selectively remove one ormore of contaminants prior to, during, and/or after combustion (e.g.,such that a given combustion product is not released into theatmosphere).

In an embodiment, combusting waste gas stream may further oralternatively comprise scrubbing, converting, and/or treating the wastegas stream, or combustion products, or combinations thereof. Asdisclosed herein, the waste gas stream may comprise volatilizedsolvents, unreacted gases, secondary products, contaminants,hydrocarbons, or combinations thereof. In an embodiment, the waste gasstream 20 may comprise may comprise hydrogen, nitrogen, methane,ethylene, ethane, propylene, propane, butane, isobutene, and heavierhydrocarbons. Ethylene may be present in a range of from about 1% toabout 40%, alternatively, from about 2.5% to about 20% by weight. Ethanemay be present in a range of from about 5% to about 50%, alternatively,from about 30% to about 40% by weight. Isobutane may be present in arange from about 1% to about 20%, alternatively, from about 1.5% toabout 5%, alternatively, from about 2% to about 3% by weight. Nitrogenmay be present in a range from about 10% to about 80%, alternatively,from about 35% to about 50%, alternatively, from about 40% to about 45%by weight.

In alternative embodiments, rather than flaring, waste stream 20 may beused as fuel (for example for steam generation or co-gen operations,and/or may be used as fuel and/or a feed to a thermal cracking unit toform ethylene (e.g., to form feed stream 10). In another alternativeembodiment, the waste gas may be exported from the plant to a monomerplant.

In an embodiment, implementation of one or more of the disclosed systems(e.g., PEP systems 100, 200, and/or 300) and/or processes (e.g., PEPprocesses 400, 500, and/or 600) may allow for the recovery of asubstantial portion of the ethylene monomers that would otherwise belost due to the operation of such systems or processes, for example, byflaring. In an embodiment, one or more of the disclosed systems mayallow for the recovery of up to about 75%, alternatively, up to about85%, alternatively, up to about 90%, alternatively, up to about 95% byweight of the ethylene monomers that would otherwise be lost. In anembodiment, one or more of the disclosed systems may allow for therecovery of up to about 75%, alternatively, up to about 85%,alternatively, up to about 90%, alternatively, up to about 95% by weightof the isobutane that would otherwise be lost. The recovery of such aportion of the unreacted ethylene monomers may yield a significanteconomic benefit, for example, by improving the efficiency of usage ofethylene monomers and decreasing capital inputs associated with theacquisition of ethylene monomers. Similarly, the recovery of such aportion of isobutane may yield a significant economic benefit, forexample, by decreasing capital inputs associated with the acquisition ofisobutene and/or by reducing the presence of isobutene in flareemissions.

In an embodiment, implementation of one or more of the disclosed systemsand/or processes may decrease the amount of ethane that is returned to apolymerization reactor (such as reactors 104 and/or 106) via a recyclestream. By decreasing the amount of ethane contained in a streamrecycled to a polymerization reactor, the overall efficiency of thepolyethylene production may be improved (for example, by increasing theethylene concentration without reaching the bubble point in the loopreactor). For example, decreasing the amount of ethane in a recycledstream may improve polymerization reactor efficiency, improve catalystefficiency, reduce polymer fouling, reduce polymerization downtime, orcombinations thereof.

A skilled artisan will recognize that industrial and commercialpolyethylene manufacturing processes may necessitate one or more, oftenseveral, compressors or similar apparatuses. Such compressors are usedthroughout polyethylene manufacturing, for example to pressurizereactors 104, 106 during polymerization. Further, a skilled artisan willrecognize that a polyethylene manufacturing process includes one or moredeoxygenators and/or similar deoxidizing apparatuses, for instancepurifying solvents or reactants and/or for purging reactors of oxygen.Because the infrastructure and the support therefore, for example toprovide power and maintain the compressors and/or deoxygenators, alreadyexists within a commercial polyethylene manufacturing plant,reallocating a portion of these available resources for use in thedisclosed systems may necessitate little, if any, additional capitalexpenditure in order to incorporate the disclosed systems and orprocesses.

Further, because compressors, deoxygenators, and various othercomponents are already employed in various polyethylene processes andsystems, the opportunity for increased operation of such apparatuses mayimprove the overall efficiency of polyethylene production systems andprocesses. For example, when a portion of a PEP process or system istaken off-line for maintenance and/or repair, other portions of thesystem (e.g., a compressor, a deoxygenator, a reactor, etc.) maycontinue to provide service according to the current processes.Operating and/or reallocating resources for operation of the disclosedPEP systems and/or processes may thereby increase the efficiency withwhich conventional systems are used.

ADDITIONAL DESCRIPTION

A process and system for the production for polyethylene has beendescribed. The following clauses are offered as further description:

Clause 1. A polyethylene production process, comprising:

-   -   contacting ethylene and a polymerization catalyst under suitable        reaction conditions to yield a polymerization product stream;    -   separating a light gas stream from the polymerization product        stream, wherein the light gas stream comprises ethane and        unreacted ethylene;    -   contacting the light gas stream with an absorption solvent        system, wherein at least a portion of the unreacted ethylene        from the light gas stream is absorbed by the absorption solvent        system;    -   removing unabsorbed gases of the light gas stream from contact        with the absorption solvent system to form a waste gas stream;        and    -   recovering unreacted ethylene from the absorption solvent        system.

Clause 2. The process of clause 1, wherein the recovering unreactedethylene from the absorption solvent system yields recovered ethyleneand further comprising contacting the recovered ethylene and thepolymerization catalyst.

Clause 3. The process of clause 1 or 2, wherein the absorption solventsystem comprises copper chloride, aniline, and N-methylpyrrolidone.

Clause 4. The process of any of clauses 1 to 3, further comprisingremoving at least a portion of elemental oxygen or oxygen-containingcompounds from the light gas stream before contacting the light gasstream with the absorption solvent system.

Clause 5. The process of any of clauses 1 to 4, wherein the contactingthe light gas stream with the absorption solvent system comprisespressurizing the light gas stream and the absorption solvent system to apressure in a range of from about 50 psig to about 250 psig.

Clause 6. The process of any of clauses 1 to 5, wherein the recoveringunreacted ethylene from the absorption solvent system comprisesdepressurizing the absorption solvent system having absorbed unreactedethylene to a pressure in a range of from about 5 psig to about 30 psig.

Clause 7. The process of any of clauses 1 to 6, wherein the light gasstream further comprises isobutene and wherein at least a portion of theisobutane from the light gas stream is absorbed by the absorptionsolvent system.

Clause 8. The process of any of clauses 1 to 7, wherein the contactingthe light gas stream with the absorption solvent system yields acomposition comprising a complex of the absorption solvent system andunreacted ethylene.

Clause 9. The process of any of clauses 1 to 8, further comprisingcombusting the waste gas stream, wherein the waste gas stream comprisesethane.

Clause 10. The process of any of clauses 1 to 9, wherein the waste gasstream comprises less than 5% unreacted ethylene by weight.

Clause 11. A polyethylene production system, comprising:

-   -   a feed stream comprising ethylene introduced into a        polymerization reactor;    -   a polymerization product stream emitted from the polymerization        reactor and introduced into a separator;    -   a light gas stream comprising unreacted ethylene emitted from        the separator, the light gas stream being separated from the        polymerization product stream and introduced into an absorption        reactor comprising an absorption solvent system;    -   an absorbent-ethylene conjugant formed within the absorption        reactor by absorption of at least a portion of the unreacted        ethylene by the absorption solvent system; and    -   a waste gas stream comprising ethane emitted from the absorption        reactor, wherein the waste gas stream comprises components of        the light gas stream that are not absorbed by the absorption        solvent system.

Clause 12. The system of clause 11, further comprising a recoveredunreacted ethylene stream emitted from the absorption reactor andreintroduced into the polymerization reactor.

Clause 13. The system of clause 11, wherein the absorbent-ethyleneconjugant is emitted from the absorption reactor and introduced into aregeneration vessel and further comprising a recovered unreactedethylene stream emitted from the regeneration vessel and reintroducedinto the polymerization reactor.

Clause 14. The system of clause 12 or 13, wherein the recoveredunreacted ethylene is recovered from the absorbent-ethylene conjugantvia a pressure reduction.

Clause 15. The system of any of clauses 11 to 14, wherein the absorptionsolvent system comprises copper chloride, aniline, andN-methylpyrrolidone.

EXAMPLES

The disclosure having been generally described, the following example isgiven as particular embodiment of the disclosure and to demonstrate thepractice and advantages thereof. It is understood that this example isgiven by way of illustration and is not intended to limit thespecification or the claims in any manner.

Prophetic Example 1

To demonstrate the effectiveness of the absorption solvent systemsdisclosed herein, a computerized commercial process simulator wasemployed to generate an output from a model in accordance with thesystems and/or processes disclosed herein. The model employed isillustrated at FIG. 7. In the model of FIG. 7, the simulation beginswith the introduction of a gaseous stream, designated VAP FEED (forexample, like the gas stream disclosed herein). The output generated bythe commercial process simulator is a material balance and a heatbalance, shown in Table 1. The names designating the various streamslisted in Table 1 correspond to streams illustrated in FIG. 7.

TABLE 1 Substream: MIXED L1CUCLL L2CUCLR L3CUCLR2 L4CUCLR3 L5CUCLL MoleFlow lbmol/hr C2═ 1.949416  41.85801   41.85801   41.85801   1.949413 C2 0.9764562 5.916248  5.916248  5.916248  0.9764532 N2 1.15E−030.1711679 0.1711679 0.1711679 1.15E−03 IC4 0.8615088 3.112527  3.112527 3.112527  0.8615092 CUCL 131.4402    131.4402    131.4402    131.4402   131.4402    ANILINE 580.5749    580.5749    580.5749    580.5749   580.5748    NMP 789.7864    789.7864    789.7864    789.7864   789.7864    Mole Frac C2═ 1.29E−03 0.0269554 0.0269554 0.02695541.29E−03 C2 6.49E−04 3.81E−03 3.81E−03 3.81E−03 6.49E−04 N2 7.64E−071.10E−04 1.10E−04 1.10E−04 7.64E−07 IC4 5.72E−04 2.00E−03 2.00E−032.00E−03 5.72E−04 CUCL 0.0873014 0.0846439 0.0846439 0.0846439 0.0873014ANILINE 0.3856129 0.3738747 0.3738747 0.3738747 0.3856128 NMP 0.52456940.5086013 0.5086013 0.5086013 0.5245694 Mass Flow lb/hr C2═ 54.68846   1174.274  1174.274  1174.274 54.68837   C2 29.36169   177.8994   177.8994    177.8994    29.3616   N2 0.0322059 4.795009  4.795009 4.795009  0.0322058 IC4 50.07382   180.9106    180.9106    180.9106   50.07384   CUCL 13012.41    13012.41    13012.41    13012.41   13012.41    ANILINE 54067.97    54067.97    54067.97    54067.97   54067.96    NMP 78293.58    78293.58    78293.58    78293.58   78293.58    Mass Frac C2═ 3.76E−04 7.99E−03 7.99E−03 7.99E−03 3.76E−04C2 2.02E−04 1.21E−03 1.21E−03 1.21E−03 2.02E−04 N2 2.21E−07 3.26E−053.26E−05 3.26E−05 2.21E−07 IC4 3.44E−04 1.23E−03 1.23E−03 1.23E−033.44E−04 CUCL 0.0894273 0.0885729 0.0885729 0.0885729 0.0894273 ANILINE0.3715804 0.36803  0.36803  0.36803  0.3715804 NMP 0.5380702 0.532929 0.532929  0.532929  0.5380702 Total Flow 1505.59  1552.86  1552.86 1552.86  1505.59  lbmol/hr Total Flow 145508    1.47E+05 1.47E+051.47E+05 1.46E+05 lb/hr Total Flow 2000    2063.515  9563.191 13833   2058.304 cuft/hr Temperature F. 90  105.0961    95.53801   140  158 Pressure psia 117.6959    114.6959    25  25  25  Vapor Frac 0 00.020591  0.0297334 0 Liquid Frac 1 1 0.9794089 0.9702665 1 Solid Frac 00 0 0 0 Enthalpy −60439.71   −58273.13   −58273.13   −56229.58  −57622.43   Btu/lbmol Enthalpy   −625.377 −615.9475      −615.9475     −594.3472      −596.2263      Btu/lb Enthalpy −9.10E+07   −9.05E+07  −9.05E+07   −8.73E+07   −8.68E+07   Btu/hr Entropy −112.3696     −109.6524      −109.5691      −106.0242      −107.4881      Btu/lbmol-REntropy −1.162701    −1.159027    −1.158146    −1.120676    −1.112192   Btu/lb-R Density 0.75276  0.7525312 0.1623788 0.1122576 0.7314713lbmol/cuft Density 72.75067   71.19494   15.36222   10.62039  70.69322   lb/cuft Average MW 96.64524   94.6073   94.6073   94.6073  96.64524   Liq Vol 60 F.  2474.029  2538.765  2538.765  2538.765 2474.029 cuft/hr Substream: MIXED L6CUCLL LKO1 LKO2 LKO3 V1 Mole Flowlbmol/hr C2═ 1.949413  2.02E−04 4.41E−03 9.89E−04 3.172776  C2 0.97645326.17E−04 8.14E−04 2.10E−04 5.654325  N2 1.15E−03 8.35E−06 8.99E−076.78E−08 7.187729  IC4 0.8615092 2.14E−04 2.23E−03 1.08E−03 0.1670439CUCL 131.4402    1.50E−13 2.85E−13 0 1.50E−13 ANILINE 580.5748   2.47E−03 0.2059512 0.0219362 2.48E−03 NMP 789.7864    2.38E−03 0.19611999.42E−03 2.38E−03 Mole Frac C2═ 1.29E−03 0.0343637 0.0107758 0.02940040.1960108 C2 6.49E−04 0.1047838 1.99E−03 6.25E−03 0.3493185 N2 7.64E−071.42E−03 2.19E−06 2.02E−06 0.4440506 IC4 5.72E−04 0.0362971 5.44E−030.032152 0.0103198 CUCL 0.0873014 2.54E−11 6.97E−13 0 9.24E−15 ANILINE0.3856128 0.4198489 0.5029009 0.6521121 1.53E−04 NMP 0.5245694 0.40328820.4788945 0.2800845 1.47E−04 Mass Flow lb/hr C2═ 54.68837   5.68E−030.1238009 0.027745  89.00829   C2 29.3616   0.0185606 0.0244775 6.32E−03170.0235    N2 0.0322058 2.34E−04 2.52E−05 1.90E−06 201.3533    IC450.07384   0.0124277 0.129461  0.0628636 9.709158  CUCL 13012.41   1.48E−11 2.83E−11 0 1.48E−11 ANILINE 54067.96    0.2303272 19.17989  2.042886  0.2311832 NMP 78293.58    0.2355062 19.44187   0.93399740.2358215 Mass Frac C2═ 3.76E−04 0.0112959 3.18E−03 9.03E−03 0.1891534C2 2.02E−04 0.0369193 6.29E−04 2.06E−03 0.3613207 N2 2.21E−07 4.66E−046.47E−07 6.18E−07 0.4279003 IC4 3.44E−04 0.0247203 3.33E−03 0.02045130.0206331 CUCL 0.0894273 2.95E−11 7.26E−13 0 3.15E−14 ANILINE 0.37158040.4581486 0.4930622 0.6646093 4.91E−04 NMP 0.5380702 0.4684502 0.49979720.3038561 5.01E−04 Total Flow 1505.59  5.89E−03 0.4095263 0.033638716.18674   lbmol/hr Total Flow 1.46E+05 0.5027346 38.89952   3.073815 470.5613    lb/hr Total Flow  2058.521 8.16E−03 0.6204605 0.04765 825.9148    cuft/hr Temperature F. 158.2431    −20    90  −20   96.94405   Pressure psia 118.6959    114.6959     24.9  24.8 114.6959   Vapor Frac 0 0 0 0 1 Liquid Frac 1 1 1 1 0 Solid Frac 0 0 0 0 0 Enthalpy−57585.8    −49592.05   −47471.61   −28177.63   −8659.402  Btu/lbmolEnthalpy −595.8472      −581.0902      −499.7715      −308.3662     −297.8729      Btu/lb Enthalpy −8.67E+07   −292.1342      −19440.87  −947.8608      −1.40E+05   Btu/hr Entropy −107.4788      −111.4813      −112.727 −110.4079      −19.64671     Btu/lbmol-R Entropy −1.112096   −1.306271    −1.186767    −1.208266    −0.6758228   Btu/lb-R Density0.731394  0.7221323 0.6600361 0.7059546 0.0195985 lbmol/cuft Density70.68575   61.62902   62.6946   64.50811   0.5697456 lb/cuft Average MW96.64524   85.34311   94.98663   91.37714   29.0708   Liq Vol 60 F. 2474.029 8.78E−03 0.6165612 0.0501975 18.42872   cuft/hr Substream:MIXED V1FLARE V2 V3 VAP-REC VAPFEED Mole Flow lbmol/hr C2═ 3.172573 39.91302   39.9096   39.90861   43.08116   C2 5.653708  4.940621 4.940017  4.939807  10.5935   N2 7.187721  0.1700194 0.1700186 0.17001857.357739  IC4 0.1668301 2.253242  2.252096  2.251014  2.417848  CUCL4.78E−22 2.85E−13 2.86E−24 0 0 ANILINE 9.19E−06 0.20608  0.022065 1.29E−04 0 NMP 3.17E−06 0.1961404 9.44E−03 2.06E−05 0 Mole Frac C2═0.1960697 0.8371173 0.843697  0.8442764 0.6789755 C2 0.3494075 0.10362230.104433  0.1045028 0.1669576 N2 0.4442117 3.57E−03 3.59E−03 3.60E−030.1159608 IC4 0.0103103 0.0472584 0.0476097 0.0476207 0.0381062 CUCL2.95E−23 5.99E−15 6.04E−26 0 0 ANILINE 5.68E−07 4.32E−03 4.66E−042.73E−06 0 NMP 1.96E−07 4.11E−03 2.00E−04 4.36E−07 0 Mass Flow lb/hr C2═89.00261    1119.71  1119.614  1119.587 1208.589 C2   170.005148.5627    148.5445    148.5382    318.5427    N2 201.3531    4.762835 4.762812  4.76281  206.1159    IC4 9.69673  130.9661    130.8995   130.8366    140.5336    CUCL 4.73E−20 2.83E−11 2.83E−22 0 0 ANILINE8.56E−04 19.19188   2.054883  0.0120247 0 NMP 3.14E−04 19.4439  0.9360284 2.04E−03 0 Mass Frac C2═ 0.1893437 0.7761549 0.79585210.797575     0.645 C2 0.3616676 0.1029799 0.1055895 0.1058162   0.17 N20.4283574 3.30E−03 3.39E−03 3.39E−03   0.11 IC4 0.0206287 0.09078230.0930468 0.0932058    0.075 CUCL 1.01E−22 1.96E−14 2.01E−25 0 0 ANILINE1.82E−06 0.0133033 1.46E−03 8.57E−06 0 NMP 6.69E−07 0.013478  6.65E−041.46E−06 0 Total Flow 16.18085   47.67913   47.30324   47.2696  63.45025   lbmol/hr Total Flow 470.0586     1442.638  1406.812  1403.738 1873.781 lb/hr Total Flow 634.7071    12547.34    11089.96     8812.544 1155.656 cuft/hr Temperature F. −20    158  90  −20    0 Pressure psia114.6959    25   24.9  24.8 226.6959    Vapor Frac 1 1 1 1 0.9823996Liquid Frac 0 0 0 0 0.0176004 Solid Frac 0 0 0 0 0 Enthalpy −9795.256 13137.72    12629.88    11470.01     5793.013 Btu/lbmol Enthalpy−337.1825        434.201 424.6725      386.242 196.1639    Btu/lbEnthalpy −1.59E+05   6.26E+05 5.97E+05 5.42E+05 3.68E+05 Btu/hr Entropy−21.92954        −18.274 −19.22263     −21.55552     −25.0739    Btu/lbmol-R Entropy −0.7548814   −0.603955    −0.6463497   −0.7258623  −0.8490563   Btu/lb-R Density 0.0254934 3.80E−03 4.27E−03 5.36E−030.0549041 lbmol/cuft Density 0.7405913 0.1149756 0.1268545 0.15928871.6214   lb/cuft Average MW 29.05031   30.25722   29.74029   29.69643  29.5315   Liq Vol 60 F. 18.41994   65.35257   64.78621   64.73601  83.15566   cuft/hr

At least one embodiment is disclosed and variations, combinations,and/or modifications of the embodiment(s) and/or features of theembodiment(s) made by a person having ordinary skill in the art arewithin the scope of the disclosure. Alternative embodiments that resultfrom combining, integrating, and/or omitting features of theembodiment(s) are also within the scope of the disclosure. Wherenumerical ranges or limitations are expressly stated, such expressranges or limitations should be understood to include iterative rangesor limitations of like magnitude falling within the expressly statedranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4,etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example,whenever a numerical range with a lower limit, R₁, and an upper limit,R_(u), is disclosed, any number falling within the range is specificallydisclosed. In particular, the following numbers within the range arespecifically disclosed: R=R₁+k*(R_(u)-R₁), wherein k is a variableranging from 1 percent to 100 percent with a 1 percent increment, i.e.,k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . 50percent, 51 percent, 52 percent . . . 95 percent, 96 percent, 97percent, 98 percent, 99 percent, or 100 percent. Moreover, any numericalrange defined by two R numbers as defined in the above is alsospecifically disclosed. Use of the term “optionally” with respect to anyelement of a claim means that the element is required, or alternatively,the element is not required, both alternatives being within the scope ofthe claim. Use of broader terms such as comprises, includes, and havingshould be understood to provide support for narrower terms such asconsisting of, consisting essentially of, and comprised substantiallyof. Accordingly, the scope of protection is not limited by thedescription set out above but is defined by the claims that follow, thatscope including all equivalents of the subject matter of the claims.Each and every claim is incorporated as further disclosure into thespecification and the claims are embodiment(s) of the present invention.The discussion of a reference in the disclosure is not an admission thatit is prior art, especially any reference that has a publication dateafter the priority date of this application. The disclosure of allpatents, patent applications, and publications cited in the disclosureare hereby incorporated by reference, to the extent that they provideexemplary, procedural or other details supplementary to the disclosure.

We claim:
 1. A polyethylene production process, comprising: contactingethylene and a polymerization catalyst under suitable reactionconditions to yield a polymerization product stream; separating a lightgas stream from the polymerization product stream, wherein the light gasstream comprises ethane and unreacted ethylene; contacting the light gasstream with an absorption solvent system, wherein the absorption solventsystem comprises copper chloride, aniline, and N-methylpyrrolidone, andwherein at least a portion of the unreacted ethylene from the light gasstream is absorbed by the absorption solvent system; removing unabsorbedgases of the light gas stream from contact with the absorption solventsystem to form a waste gas stream; recovering unreacted ethylene fromthe absorption solvent system to yield recovered ethylene; andcontacting the recovered ethylene and the polymerization catalyst,wherein the light gas stream further comprises isobutane and wherein atleast a portion of the isobutane from the light as stream is absorbed bythe absorption solvent system.
 2. The process of claim 1, wherein thecontacting the light gas stream with the absorption solvent systemcomprises pressurizing the light gas stream and the absorption solventsystem to a pressure in a range of from about 50 psige to about 250psig.
 3. The process of claim
 1. whwerein the recovering unreactedethylene from the absorption solvent system comprises depressurizing theabsorption solvent system having absorbed unreacted ethylene to apressure in a range of from about 5 psig to about 30 psig.
 4. Theprocess of claim 1, further comprising combusting the waste gas stream,wherein the waste gas stream comprises ethane.
 5. The process of claim4, wherein the waste gas steam comprises less than 5% unreacted ethyleneby weight.
 6. The process of claim 1, wherein the contacting the lightgas stream with the absorption solvent system occurs at a temperaturewithin the range of from about 0° C. to about 250° C.
 7. A polyethyleneproduction process, comprising: contacting ethylene and a polymerizationcatalyst under suitable reaction conditions to yield a polymerizationproduct stream; separating a light gas stream from the polymerizationproduct stream, wherein the light gas stream comprises ethane andunreacted ethylene; contacting the light as stream with an absorptionsolvent system, wherein the absorption solvent system comprises copperchloride, aniline, and N-methylpyrolidone, and wherein at least aportion of the unreacted ethylene from the light gas stream is absorbedby the absorption solvent system; removing unabsorbed gases of the lightgas stream from contact with the absorption solvent system to form awaste gas stream; recovering unreacted ethylene from the absorptionsolvent system to yield recovered ethylene; and contacting the recoveredethylene and the polymerization catalyst; and further comprisingremoving at least a portion of elemental oxygen or oxygen-containingcompounds from the light gas stream before contacting the light gasstream with the absorption solvent system.
 8. The process of claim 7,wherein recovering unreacted ethylene from the absorption solvent systemcomprises depressurizing the absorption solvent system having absorbedunreacted ethylene to a pressure in a range of from about 5 psig toabout 30 psig.
 9. The process of claim 7, wherein the contacting thelight gas stream with the absorption solvent system occurs at atemperature within the range of from about 0° C. to about 250° C. 10.The process of claim 7, wherein the contacting the light gas stream withthe absorption solvent system comprises pressurizing the light gasstream and the absorption solvent system to a pressure in a range offrom about 50 psig to about 250 psig.
 11. The process of claim 7,further comprising combusting the waste gas stream, wherein the wastegas stream comprises ethane.
 12. The process of claim 11, wherein thewaste gas stream comprises less than 5% unreacted ethylene by weight.13. A polyethylene production process, comprising: contacting ethyleneand a polymerization catalyst in a polymerization reactor under suitablereaction conditions to yield a polymerization product stream; separatinga light gas stream from the polymerization product stream, wherein thelight gas stream comprises ethane and unreacted ethylene; contacting thelight gas stream with an absorption solvent system in an absorptionvessel, wherein at least a portion of the unreacted ethylene from thelight gas stream is absorbed by the absorption solvent system to yield acomposition comprising a complex of the absorption solvent system andunreacted ethylene; and removing the unabsorbed gases of the light gasstream from contact with the absorption solvent system; and furthercomprising recovering unreacted ethylene from the absorption solventsystem within the absorption vessel.
 14. The process of claim 13,wherein the absoption solvent system comprises copper chloride, aniline,and N-methylpyrrolidone.
 15. The process of claim 13, wherein thecontacting the light gas stream with the absorption solvent systemcomprises pressurizing the absorption vessel to a pressure in a range offrom about 50 psig to about 250 psig.
 16. The process of claim 13,wherein the recovering unreacted ethylene from the absoption solventsystem comprises depressurizing the absorption vessel to a pressure in arange of from about 5 psig to about 30 psig.
 17. The process of claim13, wherein the contacting the light gas stream with the absorptionsolvent system in the absorption vessel occurs at a temperature withinthe range of from about 0° C. to about 250° C.
 18. A polyethyleneproduction process, comprising: contacting ethylene and a polymerizationcatalyst in a polymerization reactor under suitable reaction conditionsto yield a polymerization product stream; separating a light gas streamfrom the polymerization product stream, wherein the light gas streamcomprises ethane and unreacted ethylene; contacting the light gas streamwith an absorption solvent system in an absorption vessel, wherein atleast a portion of the unreacted ethylene from the light gas stream isabsorbed by the absorption solvent system to yield a compositioncomprising a complex of the absorption solvent system and unreactedethylene; and removing the unabsorbed gases of the light gas stream fromcontact with the absorption solvent system; and further comprisingremoving at least a portion of elemental oxygen or oxygen-containingcompounds from the light gas stream before introducing the light gasstream into the absorption vessel.
 19. The process of claim 18, whereinthe contacting the light gas stream with the absorption solvent systemin the absorption vessel occurs at a temperature within the range offrom about 0° C. to about 250° C.
 20. A polyethylene production system,comprising: a feed stream comprising ethylene, wherein the feed streamis characterized by introduction into a polymerization reactor; apolymerization product stream, wherein the polymerization product streamis characterized by emission from the polymerization reactor andintroduction into a separator; a light gas stream comprising unreactedethylene, wherein the light gas stream is characterized by emission fromthe separator, the light gas stream having been separated from thepolymerization product stream, wherein the light gas stream ischaracterized by introduction into an absorption reactor comprising anabsorption solvent system; an absorbent-ethylene conjugant, wherein theabsorbent-ethylene conjugant is characterized by formation within theabsorption reactor by absorption of at least a portion of the unreactedethylene by the absorption solvent system; and a waste gas streamcomprising ethane, wherein the waste gas stream is characterized byemission from the absorption reactor, wherein the waste gas streamcomprises components of the light gas stream that are not absorbed bythe absorption solvent system; and further comprising a recoveredunreacted ethylene stream, wherein the recovered unreacted ethylenestream is characterized by emission from the absorption reactor andreintroduction into the polymerization reactor.
 21. The system of claim20, wherein recovery of the recovered unreacted ethylene from theabsorbent-ethylene conjugant occurs via a pressure reduction.
 22. Thesystem of claim 20, wherein the absorption solvent system comprisescopper chloride, aniline, and N-methylpyrrolidone.
 23. A polyethyleneproduction system, comprising: a polymerization reactor, wherein thepolymerization reactor is configured to receive a feed stream comprisingethylene, and wherein the polymerization reactor is configured to emit apolymerization product stream; a separator, wherein the separator isconfigured to receive the polymerization product stream and to emit alight gas stream comprising unreacted ethylene, wherein the light gasstream has been separated from the polymerization product stream; and anabsorption reactor comprising an absorption solvent system, wherein theabsorption reactor is configured to receive the light gas stream, toform an absorbent-ethylene conjugant by absorption of at least a portionof the unreacted ethylene by the absorption solvent system, and to emita waste gas stream comprising ethane, wherein the waste gas streamcomprises components of the light gas stream that are not absorbed bythe absorption solvent system, and wherein the absorption reactor isfurther configured to emit a recovered unreacted ethylene stream, andwherein the polymerization reactor is further configured to receive therecovered unreacted ethylene stream.
 24. The system of claim 23, whereinthe recovered unreacted eethylene is recovered from theabsorbent-ethylene conjugant via a pressure reduction.
 25. The system ofclaim 23, wherein the recovered unreacted ethylene is recovered from theabsorbent-ethylene conjugant via a pressure reduction.
 26. The system ofclaim 23, wehrein the absorption solvent system comprises copperchloride, aniline, and N-methylpyrrolidone.
 27. A polyethyleneproduction process, comprising: contacting ethylene and a polymerizationcatalyst under suitable reaction conditions to yield a polymerizationproduct stream; separating a light gas stream from the polymerizationproduct stream, wherein the light gas stream comprises ethane andunreacted ethylene; removing at least a portion of elemental oxygen oroxygen-containing compounds from the light gas stream before contactingthe light gas stream with an absorption solvent system; contacting thelight gas stream with the absorption solvent system, wherein at least aportion of the unreacted ethylene from the light gas stream is absorbedby the absorption solvent system; removing unabsorbed gases of the lightgas stream from contact with the absorption solvent system to form awaste gas stream; recovering unreacted ethylene from the absorptionsolvent system to yield recovered ethylene; and contacting the recoveredethylene and the polymerization catalyst.
 28. The process of claim 27,wherein the contacting the light gas stream with the absorption solventsystem occurs at a temperature within the range of from about 0° C. toabout 250° C.
 29. The process of claim 27, wherein the absorptionsolvent system comprises copper chloride, aniline, andN-methylpyrrolidone.
 30. The process of claim 29, wherein the contactingthe light gas stream with the absorption solvent system comprisespressurizing the light gas stream and the absorption solvent system to apressure in a range of from about 50 psig to about 250 psig.